Phenol is most commonly produced by the Hock process. The Hock process involves alkylation of benzene with propylene to produce cumene, oxidation of the cumene to the corresponding hydroperoxide, and cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone.
Phenol can also be produced from cyclohexylbenzene. For example, cyclohexylbenzene can be produced by direct alkylation of benzene with cyclohexene, or, as disclosed in U.S. Pat. No. 6,037,513, by contacting benzene with hydrogen in the presence of a catalyst. The cyclohexylbenzene can then be oxidized to the corresponding hydroperoxide, and the hydroperoxide decomposed to phenol and cyclohexanone using an acid catalyst. The acidic catalyst will be present in the cleavage reaction mixture, and may cause corrosive damage to the process equipment, and/or may cause unwanted reactions in the downstream processing steps (e.g., separations and purifications).
U.S. Pat. No. 6,201,157 ('157 patent) generally relates to a method for producing phenol and acetone by decomposition of cumene hydroperoxide in the presence of an acid catalyst, wherein the acid catalyst is neutralized after substantial completion of the decomposition by addition of a substituted amine The '157 patent directs one to use highly hindered amines, particularly aromatic amines, in a desire to enable treatment of the acid catalyst at a high temperature without consuming the amine in a byproduct reaction with acetone. The '157 patent, and many others concerned with production of phenol starting from cumene hydroperoxide, directs one to use quite low amounts of acid catalyst (e.g., 34-38 ppm sulfuric acid), ostensibly to minimize the potential consumption of valuable acetone co-product from undesirable byproduct reactions.
The inventors have discovered that there are many differences between the manufacture of phenol starting from cumene as provided in the literature, and that starting from cyclohexylbenzene. While many of the objectives of the two processes are similar, for example, initiating a cleavage reaction with an acid while minimizing undesirable byproduct reactions, the means of accomplishing them are quite different by virtue of the substantially different stream compositions and processing steps.
The instant invention sets out methods of producing phenol starting from cyclohexyl-1-phenyl-1-hydroperoxide that go in a much different direction than the cumene literature. These include, for example, finding advantageous performance in higher levels of acid catalyst in the cleavage reaction, and lower temperatures and the use of aliphatic amines in the treatment reaction, correlated to the unique compositions in these reactions when starting from cyclohexylbenzene.
Moreover, the production of phenol and cyclohexanone from cyclohexylbenzene also produces various contaminants that are difficult to separate from the desired products. However, the nature of those contaminants and the separations involved are significantly different than those involved in either the conventional Hock process for phenol and acetone, or the conventional production of cyclohexanone from cyclohexane or phenol. For example, hydroalkylation of benzene produces significant amounts of, inter alia, cyclohexane and lesser amounts of methylcyclopentane, cyclohexene, phenylcyclohexene, and phenylcyclohexyldiene. Similarly, the oxidation of cyclohexylbenzene typically produces peroxide species alien to the Hock process, such as the desired cyclohexyl-1-phenyl-1-hydroperoxide (CHBHP), and undesired byproduct hydroperoxides such as cyclohexyl-1-phenyl-2-hydroperoxide, cyclohexyl-1-phenyl-3-hydroperoxide and cyclohexyl-1-phenyl-4-hydroperoxide. Finally, the cleavage of these various hydroperoxides produces, as both the product of the undesired hydroperoxides and the undesired byproducts of the desired CHBHP, a wide variety of contaminant species are not produced by the chemistry and technology of either the Hock process, or the cyclohexane oxidation or phenol hydrogenation processes.
Moreover, such contaminants can be particularly difficult to separate in continuous processes, and it can become increasingly more costly to separate the contaminants in the later stages (e.g., due to similarity in boiling points, etc.). As such, it would be advantageous to form compositions in the intermediate stages of the process (e.g., the compositions formed post-hydroalkylation, post-oxidation, post-cleavage, and post-neutralization) that contain a reduced or minimized level of contaminants.